Reliability Analysis of Offshore Structures

This study presents the reliability analysis of an offshore structure. The mechanical model includes various elasto-plastic diagrams with and without the combination of the normal force and the bending moment. A reduction of the normal force is introduced in order to account for buckling. A linearisation is introduced for easier application. The action of waves is represented by a Gaussian stationary and ergodic random process with zero mean value. The safety index is computed, for each failure limit state of the system, by the branch and bound method, with the help of equivalent hyperplanes in a first order approximation; a hybrid method is also developed, which requires a Monte-Carlo simulation. Two examples illustrate this approach and show that it is important to consider the bending moments for the reliability level of a system.